Defenses against ballistic missiles are currently concentrating upon the boost phase of the ballistic missile, which is a phase at which multiple warheads and/or countermeasures have not as yet been deployed. Intercepting a ballistic missile before it can deploy complicated countermeasures and/or multiple warheads greatly decreases the burden on sensors to distinguish lethal payload object(s) from countermeasures. The concept involves having interceptor assets at a location near the expected launch sites of threatening offensive ballistic missiles, sensing the presence of the threat missile soon after launch, calculating its expected trajectory, and launching interceptor asset(s) to intercept the threat missile. It will be understood that initially, a defender sensing the launch of a ballistic missile does not know exactly when it was launched, the type of missile which has been launched (although there may be some knowledge of the missile types available at the launch site), its mass, thrust, and intended trajectory. In fact, very little is initially known. Unlike engagements of threat missiles in their mid-course phase, where the trajectory of such threat missiles is well defined by Keplerian orbits, uncertainty in the trajectory of a boosting missile is a major factor in defeating such a threat missile.
Defeating threat missiles in their boost phase requires methods to filter sensor measurements and establish track states, to determine the type of a threat missile, to propagate the threat missile's state into the future, to plan an engagement against a threat missile, and to guide an interceptor to destroy the threat missile. An engagement planner for boost phase intercepts must weigh the capability of the interceptor against the uncertainty in the trajectory of the boosting threat missile.
The problem of defense against a boosting threat missile is further exacerbated by the lack of knowledge of the threat missile's trajectory, as one can only plan an interceptor missile launch if one knows which interceptor missile, among several, is in a position from which it can be expected to make a successful interception.
Missile defense arrangements that are adequate for engaging threat missile(s) in its (their) mid-course phase may not be adequate for engaging threat missiles in their boost phase. Improved or alternative boost phase missile defense arrangements are desired.